• Energy Research

Abstract Adsorption technology offers a potential in vital applications like energy storage, cooling and heating, and water desalination which can be driven by low-grade or renewable heat sources leading to significant reduction in CO2 emissions. The adsorbent material is a key element in adsorption heat pump systems determining the performance, size and cost of such technology. Metal-organic frameworks (MOFs) are class of adsorbents with superior water uptake, high pore volume and surface area. This study describes the experimental testing of adsorption heat pumps using aluminium fumarate, CPO-27(Ni) and MIL-100(Fe) for various adsorption applications. Results showed that energy storage density of 1200 W h kg−1 was achieved using MIL-100(Fe) regenerated at 95°C, and cycle time of 90 min. For cooling applications, MIL-100(Fe) showed high specific cooling power of 226 W kg−1 at 95°C while aluminium fumarate produced 136 W kg−1 specific cooling power (SCP) at 90°C. Regarding water desalination, MIL-100(Fe) showed high water production rate specific daily water production (SDWP) of 19 m3 ton−1 day−1. For power generation, including a turbine in the adsorption system can increase the effective coefficient of performance (COP) of the adsorption cooling system by 22%. Integrating the adsorption cooling system with Organic Rankine Cycle (ORC) can produce an effective COP of 0.8.

Due to the significant increase in the global temperature, the demand for cooling is dramatically rising. Most of this demand is met by conventional systems driven by electricity generated using fossil fuels contributing in the global warming phenomenon. The adsorption system is a sustainable system being driven by waste or low-grade heat sources such as solar energy. MIL-101(Cr) is a metal–organic framework (MOF) material with exceptional properties and high-water uptake. Nevertheless, it is not suitable for adsorption cooling application as the high capacity is taking place only at high relative pressure range (>0.5). The water adsorption characteristics of MIL-101(Cr) were significantly enhanced through incorporating the material with calcium chloride. Results showed that at a desorption temperature of 90°C and a chilled water inlet temperature of 10°C, the SCP increased from 168 for the neat MIL-101(Cr) to 248 and 388 W kg[sup]‒1 for Comp_1:5 and Comp_1:8 CaCl[sub]2 composites, respectively outperforming the long dominating silica gel.